I know most will say I'm full of **** but the ONLY thing I did was switch fuel.
I have tried to get it to do it again on alcohol free fuel, ideling in gear, after a long drive, on a 90 deg plus day
It just won't do it any more.
If the prospect of alcohol free gas is a no starter (proximity, cost, etc,) then the cheapest alternative would be to run a small return line back to the tank and a 3 nipple filter